Preparation of 3-methyl-2-buten-1-al

Abstract

3-Methyl-2-buten-1-al is prepared by isomerizing 3-methyl-3-buten-1-al in the presence of acidic or basic compounds. The product is a starting material for the manufacture of dyes, pesticides, pharmaceuticals, plastics and scents.

We claim: 
     
       1. A process for the preparation of 3-methyl-2-buten-1-al which comprises isomerizing the unsaturated compound 3-methyl-3-buten-1-al at from 50° to 250° C. in the presence of an isomerization catalyst selected from the group consisting of strong acids having acid exponents (pKa) of from -7 to +2.16, and tertiary amines, alkaline earth metal compounds, alkali metal compounds, ammonium compounds and tertiary phosphines as basic compounds. 
     
     
       2. A process as claimed in claim 1, wherein the isomerization is carried out at from 72° to 225° C. 
     
     
       3. A process as claimed in claim 1, wherein the isomerization is carried out at from 120° to 225° C. 
     
     
       4. A process as claimed in claim 1, wherein the isomerization is carried out with residence times of from 10 seconds to 300 minutes. 
     
     
       5. A process as claimed in claim 1, wherein the isomerization is carried out with water in an amount of from 0 to 50 percent by weight, based on the starting material. 
     
     
       6. A process as claimed in claim 1, wherein the isomerization is carried out with an organic solvent in an amount of from 0 to 50 percent by weight, based on the starting material. 
     
     
       7. A process as claimed in claim 1, wherein the isomerization is carried out with from 0.01 to 5 percent by weight of acid as the isomerization catalyst, based on the weight of starting material. 
     
     
       8. A process as claimed in claim 1, wherein the isomerization is carried out with from 0.01 to 5 percent by weight of basic compound as the isomerization catalyst, based on the weight of starting material. 
     
     
       9. A process as claimed in claim 7 wherein said acid is selected from the group consisting of sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, perchloric acid, formic acid, hydrogen chloride gas, boric acid, benzenesulfonic acid, p-toluenesulfonic acid, trichloroacetic acid, polystyrenesulfonic acid resins, phenolsulfonic acid resins and polyfluoroethylenesulfonic acids. 
     
     
       10. A process as claimed in claim 8 wherein said basic compound is selected from the group consisting of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, lithium hydroxide, lithium carbonate, sodium bicarbonate, potassium bicarbonate, calcium hydroxide, calcium oxide, barium oxide, magnesium hydroxide, magnesium oxide, barium hydroxide, calcium carbonate, magnesium carbonate, magnesium bicarbonate, magnesium acetate, zinc hydroxide, zinc oxide, zinc carbonate, zinc bicarbonate, zinc acetate, sodium formate, sodium acetate, sodium propionate, sodium butyrate, sodium isobutyrate, potassium formate, potassium acetate, potassium propionate, potassium butyrate, potassium isobutyrate sodium methylate, sodium ethylate sodium propylate, sodium isopropylate, sodium butylate, sodium isobutylate, sodium sec.-butylate, sodium tert.-butylate, sodium ethylene-glycollate, sodium 1,2-propylene-glycollate, sodium 1,3-propylene-glycollate, sodium diethylene-glycollate, sodium triethylene-glycollate, sodium 1,2-dipropylene-glycollate, potassium methylate, potassium ethylate, potassium n-propylate, potassium isopropylate, potassium n-butylate, potassium isobutylate, potassium sec.-butylate, potassium tert.-butylate, potassium ethylene-glycollate, potassium 1,2-propylene-glycollate, potassium 1,3-propylene-glycollate, potassium diethylene-glycollate, potassium triethylene-glycollate, potassium 1,2-dipropylene-glycollate, trimethylamine, triethylamine, tripropylamine, triisopropylamine, tributylamine, triisobutylamine, tri-sec.-butylamine, tri-tert.-butylamine, tribenzylamine, tricyclohexylamine, triamylamine, trihexylamine, N,N-dimethylaniline, N,N-diethylaniline, N,N-dipropylaniline, N,N-dimethyltoluidine, N,N-diethyltoluidine, N,N-dipropyltoluidine, N,N-dimethyl-p-aminopyridine, N,N-diethyl-p-aminopyridine, N,N-dipropyl-p-aminopyridine, N,N-dimethylaminoethanol, N,N-diethylaminoethanol, N,N-dipropylaminoethanol, triisopropanolamine, triethanolamine, N-methylpyrrolidone, N-ethylpyrrolidone, N-methylpiperidine, N-ethylpiperidine, N-methylpyrrolidone, N-ethylpyrrolidone, N-methylimidazole, N-ethylimidazole, N-methylpyrrole, N-ethylpyrrole, N-methylmorpholine, N-ethylmorpholine, N-methylhexamethyleneimine, N-ethylhexamethyleneimine, pyridine, quinoline, α-picoline, β-picoline, γ-picoline, isoquinoline, pyrimidine, acridine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine, quinoxaline, quinazoline, N-propyldiisopropylamine, N,N-dimethylcyclohexylamine, 2,6-lutidine, 2,4-lutidine, trifurfurylamine, triethylenediamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, diisobutylamine, di-sec.-butylamine, di-tert.-butylamine, dibenzylamine, dicyclohexylamine, diamylamine, dihexylamine, N-methylaniline, N-ethylaniline, N-propylaniline, N-methyltoluidine, N-ethyltoluidine, N-propyltoluidine, N-methylaminoethanol, N-ethylaminoethanol, N-propylaminoethanol, pyrrolidone, piperidine, pyrrolidine, imidazole, pyrrole, N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, morpholine, hexamethyleneimine, difurfurylamine, N-methylcyclohexylamine, methylamine, ethylamine, propylamine, isopropylamine, butylamine, sec.-butylamine, tert.-butylamine, benzylamine, hexylamine, cyclohexylamine, amylamine, aniline, toluidine, aminoethanol, ethylenediamine, furfurylamine, ammonium acetate, ammonium propionate, tetrabutylammonium hydroxide, trimethylbenzylammonium hydroxide, triethyl-phosphine, tri-n-propyl-phosphine, triisopropylphosphine, tri-n-butyl-phosphine, triphenyl-phosphine, tri-(2-cyanoethyl)-phosphine, bis-(2-cyanoethyl)-phenyl-phosphine and bis-(ethyl)-phenyl-phosphine.